1. Field of the Invention
The present invention relates to a scroll compressor with an improved lubrication system for a shaft seal unit.
2. Description of Related Art
The Japanese Un-Examined Utility Model Publication No. 63-43424 discloses a scroll compressor having a housing defining outer profile of the compressor and constructed by a front housing, a front end plate and a rear housing. The rear housing is formed with an inlet port for an introduction of a medium to be subjected to a compression and outlet port for a discharge of the medium after being compressed. Furthermore, to the rear housing, a stationary scroll member, which is constructed by a base plate and a scroll wall is fixedly connected. Arranged movably in the rear housing is a movable scroll member also constructed by a base plate and a scroll wall, in such a manner that a 180 degree phase difference is created between the stationary and movable scroll members, so that an outer wall side chamber is created on the outer side of the movable scroll member, and an inner wall sided chamber is created on the inner side of the movable scroll member. Furthermore, a drive shaft is rotatably supported on the front end plate by means of a seal member and a bearing member. The drive shaft has, at its inner end, a drive key, to which a drive bushing is fitted, on which bushing the movable scroll member is rotatably supported via a radial bearing, so that an orbital movement of the movable scroll member is obtained. Furthermore, a provision is also made as to means for preventing the movable scroll member from being rotated about its own axis. In this type of the compressor, the rear housing is formed with a main inlet passageway, which is in communication with the inner wall side chamber and outer wall side chamber before the chambers are sealingly closed for executing a compression operation. The prior art features that the front end plate and the rear housing form a sub inlet passageway which is branched from the main inlet passageway and which extends to the seal device.
In this type of the compressor, when a rotating movement is applied to the drive shaft from an outside source of the rotating movement, the drive key makes the drive bushing rotate. The rotation of the drive bushing is transmitted, via the radial bearing, to the movable scroll member. The self rotation blocking means prevents the movable scroll member from being rotated about its own axis, so that the movable scroll member can only execute an orbital movement. Due to the orbital movement of the movable scroll member, the inner wall sided compression chamber as well as the outer wall sided compression chamber, while the chambers are closed, are moved radially from their outermost positions to their innermost positions. At the innermost positions, both of the chambers are concentrated into a single compression chamber of a smaller volume opening to an outlet port. As a result, the refrigerant sucked from an inlet is discharged from the outlet port in a compressed condition.
In the '424 patent, the gaseous state refrigerant sucked into the chambers via the main inlet passageway is partly diverted into the shaft seal device via a sub inlet passageway. As a result, the shaft seal device is cooled by the gaseous refrigerant itself. Furthermore, the shaft seal device is lubricated by a lubricant in a mist condition included in the gaseous refrigerant. The lubricant also serves to lubricate the bearing units supporting the shaft.
However, in the prior art, the communication between the inlet port and the shaft seal unit is mainly through the sub intake passageway connecting the inlet port with the shaft seal unit. The shaft seal unit is, via gaps created between roller members in the bearing unit, also connected to the inner wall sided chamber as well as the outer wall sided chamber before they are sealingly closed for compression. However, such gaps provide a large flow resistance, on one hand, and the pressure difference between the inlet, the shaft seal device and the chambers before being sealingly closed is small, on the other hand. As a result, even after the gaseous refrigerant is contacted with the shaft seal unit, the large flow resistance as well as the small pressure difference make it difficult for the gas to be easily introduced into the inner and outer wall sided chambers. In other words, the introduction of the gaseous refrigerant into the inner wall sided compression chamber and outer wall sided compression chamber occurs only through the main intake passageway. This causes the shaft seal unit to be insufficiently cooled and lubricated, causing the lubrication of the bearing unit to be insufficient.
In view of this drawback, the Japanese Un-Examined Utility Model Publication No. 60-170088, the Japanese Un-Examined Patent Publication No. 62-132287, and the Japanese Un-Examined Patent Publication No. 2-27186 disclose compressors, wherein an oil separator or pump is provided, which allows the lubricant to be positively supplied to the shaft seal unit. However, such a provision of an oil separator or pump makes the system large, causing the installation of the system into an automobile to be difficult, on one hand, and the manufacturing cost to become high, on the other hand.